1. Field of the Invention
The present invention is directed broadly to the synthesis of an exposure image on a surface and more specifically to a system wherein electrons are passed through a plurality of apertures in a mask and are subsequently deflected to direct the image of each aperture to four successive contiguous areas on a surface.
2. Prior Art
Projection exposure schemes wherein resists are exposed through masks which project the entire image are known. Also, raster scanning utilizing a single or a plurality of electron beams which are turned on and off to synthesize images on a surface are known. The use of a light table which permits the synthesis of optical images on a photo resist surface is also known. Such a light table may be controlled from a tape to produce the desired image on the photo resist which covers a semi-conductor wafer.
U.S. Pat. No. 3,518,083 to Touchy, granted June 30, 1970 and entitled "METHOD AND APPARATUS FOR PRODUCING PHOTOLITHOGRAPHIC STRUCTURES, PARTICULARLY ON SEMI-CONDUCTOR CRYSTAL SURFACES", discloses an aperture plate containing a plurality of similar apertures through which electrons are directed to form a plurality of identical images. The mask is moved relative to the electron source along a path determined by a stylus which is following an original to produce a plurality of identical images, one per aperture, on a photo resist or the like. There is no disclosure of an exposure scheme whereby a plurality of non-identical images may be synthesized by a four step exposure-deflection of an electron beam through a plurality of rectilinear apertures.
U.S. Pat. No. 3,434,894 to Gale, granted Mar. 25, 1969 and entitled "FABRICATING SOLID STATE DEVICES BY ION IMPLANTATION", discloses a complicated arrangement utilizing a plurality of ion sources in conjunction with an apertured mask and a deflection lens system. Although Gale indicates that an electron beam source can be used with the system and indicates that the potential supply to the deflection system can cause an apparent position of the mask to shift in orthogonal directions, there is no disclosure of synthesizing a rectilinear image by a four step exposure-deflection of a beam passing through one or more rectilinear apertures in a mask.
U.S. Pat. No. 3,736,425 to Chernow provides an adjustable X-Y grid of rods to define a plurality of identical exposure areas but does not disclose an exposure scheme wherein non-identical images may be simultaneously synthesized.